Conventional grinders for scaling steel slabs and billets have a single grinding wheel mounted on the end of a boom or arm. The wheel grinds on its periphery and removes metal along a narrow path from a workpiece when the wheel is moved relative to the workpiece or vice versa. The wheel is indexed in a transverse direction as the workpiece or wheel moves back and forth to grind the entire surface of the billet or slab. This procedure is very time consuming because the wheel grinds on such a narrow path.
In accordance with this invention, multiple grinding wheels are employed. The wheels are orbited as the work and wheels move relative to one another so that the wheels grind a relatively wide path. Accordingly, much less time is required to grind the entire surface of the billet, bloom or slab than heretofore.